Separation or extraction apparatus utilizing distribution of solutes between immiscible phases

ABSTRACT

An apparatus is provided which makes use of the distribution of one or more solutes between two substantially immiscible liquid solvent phases to perform a separation or extraction. A cylindrical vessel, whose interior is subdivided by transverse partitions into a plurality of chambers each of which is in communication with its neighbours through a flow passage, is mounted for rotation with its axis horizontal. All the flow passages are located on the same side of a plane including the axis of the cylinder. Both the rotation of the vessel, and the operation of valves at the axially endmost chambers controlling supply of liquid to the vessel and withdrawal of liquid therefrom, are arranged to operate in response to a programmed control system. Supply and withdrawal of one phase at a time through the vessel can be made if the appropriate valves are opened at a time when that phase alone is presented to the flow passages in each chamber of the vessel.

United States lPatent 1191 Mueller Jan.1,1 974 1 SEPARATION OR EXTRACTllON APPARATUS UTILHZING DISTRIBUTION OF SOLUTES BETWEEN llMMISClBLE PHASES [75] Inventor: Felix Gottfried Mueller, Basel,

Switzerland [73] Assignee: Ciby-Geigy AG, Basel, Switzerland [22] Filed: Nov. 5, 1971 [21] Appl. No.: 195,916

[30] Foreign Application Priority Data Nov. 9, 1970 Switzerland ..16533/70 51 im. c1.....- B0411) 111/00 [58] Field of Search 233/19 R, 19 A, 20 R,

Primary Examiner-George H. Kn'zmanich Attorney-E. F. Wenderoth et a1.

[57] ABSTRACT An apparatus is provided which makes use of the distribution of one or more solutes between two substantially immiscible liquid solvent phases to perform a separation or extraction. A cylindrical vessel, whose interior is subdivided by transverse partitions into a plurality of chambers each of which is in communication with its neighbours through a flow passage, is mounted for rotation with its axis horizontal. All the flowpassages are located on the same side of a plane including the axis of the cylinder. Both the rotation of the vessel, and the operation of valves at the axially endmost chambers controlling supply of liquid to the vessel and withdrawal of liquid therefrom, are arranged to operate in response to a programmed control system. Supply and withdrawal of one phase at a time through the vessel can be made if the appropriate valves are opened at a time when that phase alone is presented to the flow passages in each chamber of the vessel.

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a Jllllllll ||||||||1 l lllllll IT PATENTEDJAN H974 SHEET 1n 0F 14 1. SEPARATION OR EXTRACTION APPARATUS UTILIZING DISTRIBUTION OF SOLUTES BETWEEN IMMISCIBLE PHASES FIELD OF THE INVENTION Each of one or more solutes will distribute itself between two substantially immiscible liquid solvent phases in an equilibrium depending on its partition coefficient. The present invention relates to apparatus adapted to utilise this property to perform separation or extraction of solutes.

BACKGROUND OF THE INVENTION Apparatus comprising cylindrical vessels mounted for rotation with their longitudinal axes horizontal and having their interiors divided into a plurality of intercommunicating chambers by transverse partitions have been previously proposed.

In these previously proposed arrangements flow passages between adjacent chambers were generally of one of two kinds. In one arrangement a plurality of flow apertures were uniformly distributed in each partition. In the other arrangement only a single flow aperture was provided in each partition, the flow apertures of adjacent partitions being circumferentially offset so that the totality of all flow apertures, seen over the overall length of the chamber unit, are once again distributed substantially uniformly over the vessel crosssection. In more geometrical terms, the projection of the flow apertures on to a plane normal to the rotational axis of the vessel was substantially a uniform distribution. Since all rotational positions are therefore equivalent it is not possible to influence the operation of the vessel by utilising predetermined angular positions. We have found that this prevents the suppression of flow of the upper (or less dense) liquid phase through the vessel from an inlet to an outlet, and also makes it difficult or even impossible to maintain the lower (or denser) liquid phase under steady-state conditions without losses. Furthermore, we have found that operation predictions over the long-term are possible only with some lack of accuracy and can become impossible for certain pairs of liquid phases. Since ac-. curate predictions cannot be made, programming and industrial automation are rendered impossible. A further disadvantage of this previously proposed apparatus is due to the fact that a pressure drop occurs in the upper phase as well as in the lower phase due to flow resistances which occur at the flow apertures. As a result the phase bounderies are graded in steps through the chambers in the course of a separating operation even if very small pump velocities and relatively large flow apertures are used to minimise this effect. We have found that low pump velocities result in a low rate of throughput and therefore in a poor output, and that large flow apertures cause substantial re-mixing and therefore result in lower efficiencies.

It is an object of this invention to mitigate or eliminate these disadvantages.

It is an object of this invention to provide an apparatus for utilising the distribution of one or more solutes between two substantially immiscible liquid solvent phases to perform a separation or extraction which apparatus can make use of a control program using special angularpositions of the vessel to achieve different results.

It is a further object of this invention to provide apparatus of this kind which allows enhanced throughput of selected liquid phase flow.

It is a yet further object of this invention to reduce or prevent unwanted re-mixing and thereby to enhance efficiency.

SUMMARY OF THE INVENTION In accordance with these and other objects of this invention, there is provided apparatus for utilising the distribution of one or more solutes between two substantially immiscible liquid solvent phases to perform a separation or extraction, which apparatus comprises:

a hollow vessel mounted for rotation about a horizontal axis;

a plurality of partitions disposed interiorly of said vessel transversely of said axis, and defining within the vessel a plurality of chambers for the reception of liquid;

means in said vessel defining flow passages intercommunicating adjacent chambers of the vessel, which flow passages are all disposed eccentrically of said axis and on the same side of a plane including said axis;

first and second ducting means providing separate passages for liquid transfer between the respective interiors of first and second chambers of said vessel and the exterior of the vessel;

closure means for said separate liquid transfer passages; and

control means adapted to operate said closure means in response to the angular disposition of the vessel about said axis relative to a reference position.

In a preferred embodiment the vessel is of substantially cylindrical configuration and all the flow apertures or passages are disposed in a sector subtending an angle at the axis of 45 or less. The closure means may be automatically actuated solenoid. valves, and the control means for the closure means may be programmed and also arranged to control the rotational drive of the vessel. In a preferred embodiment all the flow apertures are substantially aligned in a direction parallel to the longitudinal axis of the vessel.

The configuration of the vessel defines two important angular zones. In one of these two zones only the upper liquid phases of adjacent chambers communicate, while in the other only the lower liquid phases of adjacent chambers communicate. Flow of liquid in the axial direction may be arranged to take place either only in the. upper or in the lower phase. Accordingly, a flow of one phase only .can be produced by a pressure gradient alone provided it is applied at an appropriate time. Displacement of the phase which is not to be transferred can be made impossible by operation of the closure means in response to the control means, and appropri-' ate programming ensures that the phase which is not to be transferred during the time interval concerned is completely enclosed in the vessel. The closure means are therefore not merely aids for controlling the supply or discharge of the liquid phases into or from the vessel but, in'cooperation with the specially disposed flow passages and the control means also ensure a positively controlled phase flow and therefore a constant phase ratio. Furthermore, the rotation of the vessel is utilised not only for adjusting the distribution equilibrium but also for controlling the liquid phase flows. By contrast to previously proposed apparatus, embodiments constructed in accordance with this invention have their vessel filled to a much higher level or even completely. This results in an improvement of the ratio between occupied space and attainable throughput.

The vessels of embodiments of the apparatus in accordance with this invention may be enclosed in completely air tight manner. It is therefore possible to operate in an inert gas atmosphere, under conditions of very low gas consumption, a feature which is of particular importance when it is necessary to operate with solute components which are readily oxidisable.

Embodiments of apparatus according to the invention may be provided without difficulty with a regulator for controlling the liquid phase flow ratio. To this end, two sampling chambers of the vessel, disposed symmetrically relative to a feed chamber of the vessel, are tapped and small quantities of the upper or lowerphase are pumped continuously or at certain intervals from the aforementioned two chambers through two detectors selected in accordance with the appropriate analytical problem and then returned into the same sampling chamber. The two measured values thus obtained are compared with set values. The difference signals produced by the comparison between measured and set values are utilised for the automatic follow-up control of the phase flow ratio.

The flow apertures are preferably disposed in configurations with the maximum possible eccentricity from the axis of the vessel. The phase ratio may thus be selected substantially without restriction (p 0.1 This isparticularly important for operation with a stationary phase.

Positive pressures of the order of magnitude of 0.1 atm gauge are used to cause flow. The flow apertures may therefore be kept relatively small (diameter l 4 mm) even if the throughput rates are substantial. This eliminates practically all re-mixing. The efficiency in operation is therefore high. Longitudinal mixing due to convection or diffusion may thus be substantially avoided even during prolonged periods (months) when the apparatus is shut down.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1a is a diagrammatic illustration of one embodiment of apparatus'in accordance with this invention;

FIG. lb is a side view of the apparatus of FIG. la as seen in the direction of the arrows lb 1b of FIG. la

FIGS. 2 to 8 show seven different variations for the interior construction of the vessel, ach being shown as a partial axial section;

FIGS. 8a 8b and 80 show separate sections along the lines VIIIa, VIIIb amd Vlllc of FIG. 8; and

FIGS. 9 to 17 are graphs to explain methods of operation of the entire system of FIGS. 1a and lb.

DESCRIPTION OF THE PREFERRED EMBODIMENTS vessel is provided with ducts and/or pipelines, identifled by the same reference numerals, which cooperate with the stationary pipelines. These latter ducts and/or pipelines rotate with the cylindrical vessel 20 and are in communication with the stationary pipes through stationary, hollow cylindrical housings 350, 351 in which the stub extensions 250, 251 are arranged to rotate in the manner of a gland and appropriate annular grooves. Such arrangements are usually referred to as rotary seal bushings. Each of the stationary pipes 200 205 is connected through a solenoid valves 220 225 and pumps, which are not shown, to vessels which are also not shown.

The cylindrical vessel '20 is provided with two circular end discs 50, 51 which sit on rollers 52 55 which in turn are supported by means of bearing pedestalsSS and 59 to run freely relative to the machine bed 60. The cylindrical vessel may be driven by the arrangement shown in FIG. 1b in which a motor drives a belt drive comprising belt pulleys 192 and 193 and a toothed belt 194, via a continuously variable transmission 191.

The cylindrical vessel 20 is hollow and its interior is sub-divided into a plurality of chambers by means of transverse partitions or bulkheads 210 which are disposed at right angles to the axis of the cylinder in the preferred arrangement. The resultant chambers 206, 207, 208, 209 etc., have radial dimensions much greater than their axial dimensions and adjacent chambers communicate with each other through flow passages 211. All the flow passages 211 are radially offset from the longitudinal axis of the cylindrical vessel and on the same side of a plane including the longitudinal axis. Preferably all the flow passages lie within a cylindrical sector subtending an angle smaller than 45 at the axis. Different configurations for the flow apertures are illustrated in FIGS. 2 8.

In the arrangements of FIGS. 2, 3 and 4, all the flow passages 211 comprise apertures in the partitions or bulkheads which are disposed in a straight line which is parallel to the longitudinal axis of the vessel, i.e. they are radially offset at equal distances from the longitudinal axis, baffles being disposed between the said flow apertures in order to suppress the so-called coanda effect. In the embodiment shown in FIG. 2, each of these baffles comprises a circular disc 40 in each chamber; in FIG. 3 each baffie comprises a centrally perforated disc 41 in each chamber; and in FIG. 4 each comprises a labyrinth sequence of circular discs 40 and centrally perforated discs 41. In the embodiment of FIG. 5 a separate closing element is associated with each flow aperture 211. In the illustration each of the closing elements is represented by a small disc 42, all of which discs are fixedly threaded to a common rod 43. Displacement of the rod 43 enables the flow apertures 211 to be partially or wholly closed. In the opened position the discs 42 function as baffles.

In the embodiment of FIG. 6, all the flow passages 211 are disposed on a straight line, the flow passages being constructed as inclined ducts in order to prevent the coanda effect.

In the arrangement of FIG. 7 the flow apertures 211 are radially offset at different distances from the longitudinal axis but are all disposed in the same plane including the longitudinal axis of the vessel.

In the embodiment of FIG. 8, alternate flow apertures 211 are offset from a reference plane including the longitudinal axis of the vessel. As shown in the sectional views of FIGS. 8a to 80, alternate offset flow apertures are offset to the left and to the right whereby to define angles of offset +0: 0: subtended at the axis. We have found that the angles of offset should be only sufficiently large to just avoid the coanda effect. As a rule an angular offset of 10 to is found to be sufficient. The angle of offset feature of the FIG. 8 embodiment may be combined with the radial offset feature of FIG. 7. The cylindrical vessel may be constructed as described in Swiss Patent specification No. 433,199 from rings of stainless steel, plastics or the like and perforated plates which are alternately stressed together. It is also possible for circular plates which form the partitions or bulkheads to be located at a distance by means of a central mandrel or the like and for a hose of suitable material, for example plastics, such as polytetrafluoroethylene-propylene or the like and to be shrunk on to the structural component thus formed.

During operation of the apparatus, the cylindrical vessel with a charge comprising the two liquid phases concerned and the particular solute is rotated about its longitudinal axis at a rate of between 5 and 50 rev/min in order to adjust the distribution equilibrium of the solute concerned between the two solvent phases. A constantly renewing liquid film of that phase with better wetting properties is produced on the chamber bulkhead in the course of this rotation and, where they are present, also on the baffles. The resultant large area of contact between the two phases ensures that the distribution equilibrium is rapidly obtained.

Closure means, preferably in the form of solenoid valves 220-225, are provided for the pipelines 200-205; and programmable control means, designated generally by the letters ST in FIG. 1, are provided for operating the closure means in response to the angular disposition of the vessel about its longitudinal axis relative to a reference position. In other words the opening times of the valves 220 225 may be controlled in dependence on the angular positions of the flow passages 211 in the manner required for any selected mode of operation of the apparatus.

In the. illustrated embodiment the control means ST comprises seven timers 1 7, three counters 13 15, a resetting unit 30, an angular setting encoding unit 31, a storing indicator unit 12, a contactor control system 17, a programming unit 16 and a, stabilised dc voltage source 32 operated from a power line. The power line connection is designated by the letter N.

The control means ST is connected by way of the encoding unit 31 to apparatus which scans the rotational disposition of the cylindrical unit-20. In the illustration the rotational scanning unit comprises two microswitches 24 and 25, the actuating elements of which are disposed in the path of at least one respective cam 22, 23 which cams are disposed on a stub extension 21 of the cylindrical unit.

The programming unit 16 is preferably constructed as a printed circuit, and connects different stages of the control means to each other and to the control windings of the solenoid valves 220 225 depending on the particular program selected.

Each ofthe timers 1 7 is provided with a potentiometer 71 to 77, respectively to enable its operating period to be adjusted and may be triggered by depressing a start button 91 to 97, respectively, or by feeding an electric pulse to a terminal 701 to 707, respectively. It will be'a ppreciated that a pulse is delivered through the respective terminal whenever its associated start button is depressed. The time to which the potentiometers 71 to 77 respectively are set begins to run down at the moment of triggering. At the same time a relay 101 to 107 respectively is energised to close a pair of contacts 301 to 307 respectively. Each of these pairs of contacts is arranged to be opened when the time set by the potentiometers 71 to 77 respectively has elapsed. At this moment of time an electric pulse is arranged to be delivered from a pulse output 901 to 907 respectively. The pairs of contacts 301 to 307 respectively may be closed independently of the state of their associated timer 1 to 7 respectively by closing a switch 601 to 607, respec tively, provided for manual operation. The manual control therefore has priority over the automatic control.

Each of the counters 13, 14 or 15 may be reset to .zero by means ofa push-button 27,. 28, 26. The counter 13 is constructed as a preselector counter.

The contactor control system 17 controls the entire power supply. Closing ofa switch 98 causes a contactor 99 to be energised and to close its contacts. This in turn results in connection of the dc voltage source and in disconnection of the feed to the motor 190 through two contactors and 180. The contactor 170 is provided for reversing the polarity of the motor feed and therefore defines the direction of rotation of the motor 190. Contactor 170 is controlled by the timers 1 and 3. The contactor is provided for switching the motor on and off and is controlled by the encoding state 31 through a conductor 34 and by the timers 3 and 4. A gate circuit, contained in the, encoding stage 31, and a bistable stage ensure that in intermittent operation the control contactor 180 becomes inoperative after activation of the timer 1 only when cam 23 closes switch 25. Until this time is reached the control winding of contactor 180 will remain energised through conductor 34. However, if timer 2 is activated, the contactor 180 is becomes inoperative only if cam 22 closes switch 24. The encoding stage 31 ensures that, during continuous operation, the timers 5, 6 (and, where appropriate the timer 7) are activated only if the cylindrical unit 20 is in a defined position which is suitable for a desired transfer of a liquid phase through the unit. The counter 15, actuated by a pulse from the resetting unit 30, counts the number of complete machine cycles.

Separate indicating elements 401 to 407 respectively are associated with the timers 1 '7 in the storing indicator unit 12. In order to save space, each of the storing indicating elements is represented as a box with a lamp disposed therein. The box symbolises a bistable stage which is adapted to switch the lamp. A pulse, arriving from the associated timer, sweeps each of the bistable stages into the position in which the lamp is switched on and in which position it remains until a pulse from the position indicated in the circuit of the programming unit by the numeral 444 in FIG. la arrives at the second input. The operating state of the apparatus at any time is therefore indicated in the lamp section 401 407. The bistable stage may be formed by a self-locking relay or latch relay. The use of such a relay offers the advantage that the last operating stage prior to the interruption is automatically indicated at the end of the interruption by a memory and function indication. A resetting pulse from the resetting stage 30, supplied automatically at the end of a complete program sequence or provided manually by depressing a resetting button 11 sweeps back 'the bistable stages and thus extinguishes the lamps that were previously switches on. Two preferred angular rotational positions of the chamber unit will be designated in the functional description hereinbelow as horizontal position" and zenith position respectively. In the horizontal position all flow apertures 211 are disposed either in the horizontal plane including the longitudinal axis of the cylindrical vessel (as in theembodiments shown in FIGS. 2 7) or are disposed symmetrically with respect thereto (as in the embodiments shown in FIGS. 8 and 8a 80). In the zenith position all flow apertuees 211 are disposedabove the said horizontal plane either in the vertical plane including the longitudinal axis of the vessel (as in the embodiments of FIGS. 2 7) or symmetrically relative to this vertical plane (as in the embodiments of FIGS. 8 and 8a 80).

Prior to each operation the cylindrical vessel is filled with both liquid phases (of which, we shall refer to the relatively denser liquid as forming the lower phase and the relatively less dense liquid as forming the upper phase). To this end the valve 220 is connected to means for the supply of the lower phase to the unit and the valve 221 is connected to means for supply of the upper phase to the unit. Each of the two feed means comprise a supply vessel and a pump; such means are well known per se and are therefore not shown. To perform a charging operation of the lower phase, the buttons 93 or 94 are depressed until the motor 190 has rotated the cylindrical vessel into its horizontal position. The button 96 is depressed in the horizontal position. This causes the valves 220 (lower phase supply valve) and 225 (discharge valve) to be opened. The button 96 is depressed or interlocked until the unit is filled with the lower phase to the level of the flow passages 211. After the button 96 is released, thus causing the valves 220 and 225 to be closed again, the buttons 93 or 94 are depressed or interlocked until the motor 190, thus switched on, has rotated the cylindrical vessel into its zenith position. In the zenith position the valves 22] (upper phase supply valve) and 224 (discharge valve) are opened by depressing the button 95 until the remaining volume of the cylindrical vessel is filled with the light phase, apart from a small air cushion which will remain above the flow apertures if no further precautions are taken.

Before being charged with liquid, the vessel is flushed.

with an appropriate gas if it is desired to operate in an inert gas atmosphere. The vessel is evacuated prior to filling if it is desired to operate with a completely filled vessel. The cylindrical vessel is then moved into the zenith position and the lower phase is drawn in, pumping being continued at the lower phase outlet. When the cylindrical vessel is completely filled in this manner with lower phase, the supply and discharge valves for the lower phase are closed, the vessel is then rotated into the horizontal position and, while the upper phase valves are opened, a portion of the lower phase is displaced by the upper phase. Vessels of relatively large size are preferably provided with venting means for each chamber and may then be completely filled without difficulty (that is to say without resorting to the use of vacuum means) when the venting means are open.

The apparatus will operate in the following manner after charging of the cylindrical unit when the programming unit 16 of FIG. 1 is employed.

Depressing the start button 93 starts the timer 3. The relay 103 energises and closes the contact 303. At the same time the indicating element 403, associated with the timer 3, is switched on. The contactor 170, which defines the direction of rotation of the motor 190, and the contactor 180, which controls the on-and-off switching of the said motor, is brought into the position shown in the drawing.

The motor 190 rotates the cylindrical vessel 20 in th clockwise direction via the transmission 191 and the belt drive 192, 193, 194. The timer 3 is swept back into its zero positionat the end of the period of time to which the potentiometer 73 of the timer 3 has been set. Accordingly, the relay 103 then opens its contact 303. A pulse appears at the pulse output 903 and passes through the programming unit 16 to the pulse input 701 of the timer 1. This causes the timer 1 to be started and its relay 101 closes the contacts 301. Accordingly, the contactor continues to remain in the illustrated position. The contactor is energised by the encoding stage 31 only until the cam 23 closes the switch 25. Cam 23 and switch 25 .are disposed relative to the axis of rotation of the cylindrical vessel so that the flow apertures are in the zenith position when the switch 25 is closed. The motor is therefore stopped when the cylindrical vessel is in the zenith position. The relay 101 opens its contact at the end of the period of time to which the timer 1 or its potentiometer 71 is set. Accordingly, the contactor 170 then reverses the polarity of the feed for the motor 190 to produce an opposite sense of rotation of the unit (in the counter-clockwise sense in this specific example). A pulse will then appear at the pulse output 901. This pulse is transferred through the programming unit 16 to the pulse input 705 of the timer 5 and also switches on the indicating element 405. This in turn causes the timer 5 to be started. The relay 105 will be energised to close its contacts 305. The upper phase valves 221 (supply) and 224 (discharge) will then be energised and remain open while the timer 5 runs down. Upper phase is fed into the chamber 207 through the duct 201 during this period of time. An identical quantity of upper phase is discharged from the chamber 208 through the duct 204 and is collected, for example in a fraction collector (not shown). The relay 105 is de-energised and opens its contacts 305 after the time 5 has run down. The valves22l and 224 are thus once again closed. The pulse passes from the output 905 through the programming unit 16 and a selector switch 131 of the preselector counter 13 to the pulse input 704 of the timer 4. This causes the said timer to be started and the associated indicating element 404 to be switched on. The relay 104 closes its contacts 304 so that the contactor 180 is energised. While the timer 4 runs down, the motor 190 rotates the cylindrical vessel in the counter-clockwise direction. (Reversal of the motor avoids undesirable pumping'effects which are the result of installation inaccuracies. Pumping effects of this kind would result in a detrimental shift of the boundary between the two phases in individual chambers of the vessel. Avoidance of such installation inaccuracies is generally too costly.) After the timer 4 has run down, the relay 104 opens its contacts 304. A pulse passes from the pulse output 904 through the programming unit 16 to the pulse input 702. This starts the timer 2 and accordingly causes the indicating element 402 to be switched on. The relay 102 is energised and closes its contacts 302.

9 The hold signal for the contactor 180 is maintained by the encoding unit 31 through a conductor 33 on the conductor 34 until the cam 22 closes the switch 24. At this moment the contactor 180 will interrupt the motor current. The motor 190 stops the rotation of cylindrical unit 20 with theflow apertures 211 being disposed in I the position opposite to the zenith position. After the timer has run down a pulse passes from the pulse output to the pulse input 706 of the timer 6. This causes the said timer to be started and accordingly causes the indicating element 406 to be switched on. At the same time the relay 106 closes its contacts 306. The lower phase valves 220 and 225 will then be energised and remain open while the timer 6 runs down. During this period of time lower phase is fed through the duct 205 into the chamber 208. A quantity of lower phase, corresponding to that supplied, leaves the cylindrical vessel 20 through the duct 220 and is preferably also collected in a fraction collector (not shown). The valves 220 and 225 are closed at the moment'of time at which the timer 6 has run down. The pulse which appears at the output 906 is transferred to the resetting unit 30,

where it is converted intoa pulse of defined shape and length which is then transferred through a conductor 330. This pulse extinguishes all indicating elements 401 407, increases the count in the counters l3 and by one and starts the timer 3 through its pulse input 703. A new cycle, corresponding to the preceding cycle will then begin. These cycles will be repeated until the counter 13 reaches a preselected number. The counter 13 then reverses the switch 131 for the next cycle when this event occurs. This ensures that when the timer 5 has run down, its pulse output 905 will supply a pulse through the programming unit 16 to the pulse input 707 of the timer 7. This in turn causes the timer 7 to be started. As a result, the indicating element 407 is switched on and the relay 107 closes its contacts 307. Closing of the contacts 307 causes the valves 222 and 223 to be opened. Samples may be obtained from intermediate chamber 209 through the ducts 202 and 203 and may be returned after analysis while the timer 7 runs down. At the moment at which the timer 7 runs down its pulse output 907 delivers a pulse to the pulse input 704 of the timer 4 so that the cycle which has just been completed is normally continued. The next reset ting pulse of the resetting unit 30 sets the counter 13 to zero, the switch 131 again moves back into the illustrated position and the counter 14 is provided with a counting pulse through the conductor 132.

All the operations may be performed automatically by appropriate interchanging of programming units 16. Some important variations will be described hereinbelow by reference to the graphs of FIGS. 9 to 17. In the graphs of FIGS. 9 to 17 the following functions are plotted in lines a p with respect to time t. In line a the pulses of the encoding unit 31, in lines b h the output signals of the timers l 7, in lines in the positions with respect to time of the valves 220 to 225, in line 0 the starting pulses supplied to the terminals 901 907 of the timers l 7 and in line p the resetting pulses supplied by the resetting unit 30. In lines 1 to n two reference positions are shown: a closed valve is indicated by the lower reference position and an open valve by the upper reference position. All graphs commence from the end of a charging of the cylindrical vessel.

The graph of FIG. 9 shows the conditions of operation over a period of time when the upper phase is mobile and the lower phase is stationary. The mixture to be separated, dissolved in some of the upper or lower phase solvent is introduced as a liquid charge into the vessel by operation of supply and discharge valves (221 and 224) while the cylindrical vessel is stationary. With the valves closed, the vessel is then rotated until equilibrium of partition of solute between the two phases is obtained. After the cylindrical vessel has been brought to a stop so that the flow passages are in the position opposite to the zenith position, elution through the upper phase will begin after a possible pause for separation of the phases from each other. To this end one of the sets of supply and discharge valves (221, 224) is opened until approximately one tenth of the upper phase volume of one chamber is transferred. This is followed by a fresh cycle. The individual components of the mixture may be collected at the upper phase discharge (valve 224) as a series of successive concentration peaks (which follow quasi Gauss distribution curves) since the individual components traverse the cylindrical unit at different rates corresponding to their different Nernst distribution coefficients. Slowly travelling impurites may be removed from the chamber unit on completion of the separation process by virtue of the polluted lower phase being displaced by fresh lower phase when the upper phase is in a steady-state and the apparatus is stationary in the position opposite to the zenith position.

The graph of FIG. 10 illustrates the operation of the process over a period of time when the lower phase is mobile and the upper phase is stationary. In this variation of operation the cycle is the same as previously explained with reference to FIG. 9, except that in place of the upper phase valves (221, 224) the lower phase valves (225, 220) are opened whenever the flow apertures are in their position opposite to the zenith position. Slowly traversing impurities'may of course also be removed from the apparatus by partial replacement of the upper phase after completion of the separation operation.

Since both phases may be optionally set in motion, it is possible to obtain separations with pairs of phase in which the components of the mixture travel only very slowly with the upper phase through the apparatus owing to small distribution coefficients (k 1), such separations being performed with a steady-state upper phase and a mobile lower phase.

The graph of FIG. 11 shows the operation conditions over a period of time when phases move in the same senses.

If it is desired to perform repeated and successive separation in which slowly travelling impurities must be washed out in accordance with one of the modes of 7 operation shown in the graphs of FIGS. 9 or 10 (use of the apparatus in the sense of a preparational gas chromatrograph) it is possible to employ the following procedure: elution in accordance with the graph of FIG. 9 or 10 and interposition of an additional step in which the other phase is conveyed in the same direction but at a much lower throughput rate. The complete cycle will then include the following (if the FIG. 9 rather than FIG. 10 procedure is followed): rotation of the cylindrical unit until equilibrium is obtained, pause, normal upper phase transfer, rotation until equilibrium is once again obtained, pause, transfer of a small quantity of lower phase. v 

1. Apparatus for utilising the distribution of one or more solutes between two substantially immiscible liquid solvent phases to perform a separation or extraction, which apparatus comprises: a hollow vessel mounted for rotation about a horizontal axis relative to a reference rotational position; a plurality of partitions disposed interiorly of said vessel transversely of said axis, and defining within the vessel a plurality of chambers for the receiption of liquid; means in said vessel defining flow passages intercommunicating adjacent chambers of the vessel, which flow passages are all radially offset from said axis and on the same side of a plane including said axis; first and second ducting means providing separate liquid transfer passages between the respective interiors of first and second chambers of said vessel and the exterior of the vessel; closure means for said separate liquid transfer passages; and control means coupled to said closure means for operating said closure means in response to the rotational disposition of the vessel about said axis relative to said reference position.
 2. Apparatus according to claim 1, wherein said vessel is of generally cylindrical configuration and is mounted for rotation about its longitudinal axis, and wherein all said flow passages are located in a sector subtending an angle of about 45* or less at said longitudinal axis.
 3. Apparatus according to claim 2, wherein all said flow passages are disposed approximately in a straight line parallel to said longitudinal axis.
 4. Apparatus according to claim 2, wherein alternatE flow passages are offset on opposite sides of a plane including said horizontal axis.
 5. Apparatus according to claim 2, wherein alternate flow passages are radially offset at different distances from said axis.
 6. Apparatus according to claim 1, wherein the direction of entry of each of the flow passages into its associated chambers is inclined.
 7. Apparatus according to claim 1, wherein at least one baffle is disposed in the path between the two flow passages of each chamber.
 8. Apparatus according to claim 1, wherein said control means comprises means to open said closure means for a defined interval during each nth (n 1, 2 or 3 etc.) rotation of the vessel, said time interval being disposed entirely in a time period during which all the flow passages are disposed in the upper half of the vessel.
 9. Apparatus according to claim 1, wherein said control means comprises means to open said closure means for a defined interval during each mth (m 1, 2 or 3 etc.) rotation of the vessel, said time interval being disposed entirely within a time period during which all the flow passages are disposed in the lower half of the vessel.
 10. Apparatus according to claim 1, wherein said first and second chambers comprise the axially endmost chambers of the vessel and at least one intermediate chamber is also provided with ducting means providing a passage for liquid transfer between the interior of said intermediate chamber and the exterior of the vessel, closure means being provided for said intermediate liquid transfer passage which closure means are operable by said control means.
 11. Apparatus according to claim 10, wherein said closure means include separately adjustable timing means for adjusting the duration of the individual opening periods for the closure means.
 12. Apparatus according to claim 1, wherein the control means comprises means to interrupt the opening of the closure means for a predetermined number (M> 1) of rotations of the vessel after another predetermined number (N> 1) of rotations has taken place.
 13. Apparatus according to claim 1, wherein the control means comprises means to stop the rotation of the vessel for a predetermined period of time in an angular position in which the flow passages are symmetrically disposed with respect to the vertical plane including said axis and for opening said closure means for a predetermined time period during the aforementioned stopping period.
 14. Apparatus according to claim 1, wherein both said first and second ducting means provide two passages for liquid transfer between the interiors of their respective chambers and the exterior of the vessel each said passage having a closure means and each such closure means being operable by said control means, for to alternately opening one closure means of each of said first and second chambers for a predetermined number of rotations of the vessel at each nth (n 1, 2 or 3 etc.) rotation for a predetermined time interval while maintaining the other closure means of each of said first and second chambers in its closed position.
 15. Apparatus according to claim 1, wherein said first and second chambers comprise the axially endmost chambers of the vessel and an intermediate chamber is also provided with ducting means providing a passage for liquid transfer between the interior of said intermediate chamber and the exterior of the vessel, closure means being provided for said intermediate liquid transfer passage which closure means are also operable by said control means; and wherein said control means opens the axially endmost chamber closure means for a defined time interval during each nth (n 1, 2 or 3 etc.) rotation of the vessel, said time interval being disposed entirely in a time period during which all the flow passages are disposed in the upper half of the vessel.
 16. Apparatus according to cLaim 15, wherein the intermediate chamber ducting means provides two passages for liquid transfer between the interior of said intermediate chamber and the exterior of the vessel, each said passage having a closure means, and each such closure means being operable by said control means for opening both said intermediate chamber closure means during each qth rotation of the vessel for a defined time interval, which time interval is disposed entirely in a time period during which all the flow passages are disposed on the same side of the horizontal plane including the axis of rotation of the vessel.
 17. Apparatus according to claim 1, wherein the flow passages are provided with valve means and valve actuating means coupled thereto for actuating said valve means simultaneously.
 18. Apparatus according to claim 1, wherein said closure means include separately adjustable timing means for adjusting the duration of the individual opening periods for the closure means. 